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  • Class a over class a/b sound

    are tubes Amos always class A ?
    What does class a sound as opposed to class a/b some claim the first few watts of class a Ina class a/b sound better and one can hear the change
    i know some On my way! Massive pure class a amps why can someone please explain also if it's better why don't more companies make them.
    Goldman comes to mind making very expensive devices but I don't recall them making any .
    A little inside info please .

  • #2
    Biggest argument against Class A amps is their inherent inefficiency. They run at full power at idle. They actually cool down when run hard. Most Class A amps used to be low power (probably 25 watts or less) and high power Class A amps not only consume tremendous amount of power, but their designs will always make them very expensive.
    Steve Lefkowicz
    Senior Associate Editor at Positive Feedback
    --------------------------------------------------------
    http://www.audionirvana.org/forum/ti...ounding-system

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    • #3
      Class A is the purest sound, but it comes at a heavy price in terms of heat and 'wasted' energy due to the inefficiency of Class A designs. They are more expensive to build for a given wattage. All of these reasons factor into why most amps are Class A/B and why more of them aren't manufactured. And no, tube amps aren't almost always Class A. Rather, they are almost always Class A/B.
      SP-10 MKII table with custom power supply designed and built by Peter Noerbaek, SME 312S arm, Dyna XV-1S cartridge, Zesto Andros 1.2 phono stage, Otari MX-55 tape deck, Ampex 350 repros, ARC Ref 6 pre, ARC Ref 75 amp, and NOLA KO speakers with a pair of Def Tech Ref subs.

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      • #4
        All great answers n a big thanks but how about the sound in both pure and a/b when they SW over ?

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        • #5
          there's a subliminal connotation, i believe, between the term "Class-A" and "grade-a" with the inference that it's "better than" or "best." by fair means or foul, this is the message conveyed because some 'philes that claim its superior can't even define what it means or how class A/B is different. I've owned amps with both topologies and I like both, coincidently the one's that stayed in my system the longest happen to be A/B. IMHO there's no hard fast rule that one topology is clearly superior to the other.
          TT / Arm / Cart: Basis Audio Ovation / Rockport 6000 / VdH Colibri XCP Head Amp: Music Reference RM-4 Preamp: Audio Research SP-3 (Curcio) Power Amp: Marantz 8b Speakers: 1) Quad ESL 57 (McCollum) 2) Falcon LS3/5a / SVS PC-2000 (x2) Cable: DIY / Canare / Mogami / DH Labs

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          • #6
            Originally posted by mep View Post
            Class A is the purest sound, but it comes at a heavy price in terms of heat and 'wasted' energy due to the inefficiency of Class A designs. They are more expensive to build for a given wattage. All of these reasons factor into why most amps are Class A/B and why more of them aren't manufactured. And no, tube amps aren't almost always Class A. Rather, they are almost always Class A/B.
            Just a question, but aren't all single ended tube amps Class A? I'm not sure on that but I remember reading that somewhere a long time ago.
            Steve Lefkowicz
            Senior Associate Editor at Positive Feedback
            --------------------------------------------------------
            http://www.audionirvana.org/forum/ti...ounding-system

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            • #7
              Thanks all for the feed back as in hi end audio myths left alone long enough become facts
              my krells and now my Aragon's stay hot meaning they do begone in class a
              now if I play low or loud I cannot determine any change
              I also use many headphones with both tube and SS Amps
              i do not recall a thread on class a or a/b for them
              I can email Baskin king and ask him. I know when paul
              of ps audio released his new Amps both him and Arnie touted how many watts it played before it crossed over to a/b claiming hiw much of our music can be played in class a with there new Amps. Again no actual description lol
              many myths in digital I can debunk or others can
              but when something like this is claimed and it's purely about hearing it who do you beleave ?

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              • #8
                Originally posted by Steve Lefkowicz View Post

                Just a question, but aren't all single ended tube amps Class A? I'm not sure on that but I remember reading that somewhere a long time ago.
                Yes, all SE tube amps have to be Class A by design. Most SE tube amps have one output tube per channel and it has to amplify both halves of the waveform. Even when you have a SE amp with multiple output tubes for increased power, they are still amplifying both halves of the waveform. I should have made that clear.
                SP-10 MKII table with custom power supply designed and built by Peter Noerbaek, SME 312S arm, Dyna XV-1S cartridge, Zesto Andros 1.2 phono stage, Otari MX-55 tape deck, Ampex 350 repros, ARC Ref 6 pre, ARC Ref 75 amp, and NOLA KO speakers with a pair of Def Tech Ref subs.

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                • #9
                  Originally posted by Alrainbow View Post
                  are tubes Amos always class A ?
                  What does class a sound as opposed to class a/b some claim the first few watts of class a Ina class a/b sound better and one can hear the change
                  i know some On my way! Massive pure class a amps why can someone please explain also if it's better why don't more companies make them.
                  Goldman comes to mind making very expensive devices but I don't recall them making any .
                  A little inside info please .

                  In SS, good ones like Vitus, at a lower price Symphonic Line Kraft, older Krell FPBs, the Luxman m800s, Lamm 1.2, got their liquidity and fluidity through that class A sound. Vitus is a very good example. Some like the new Luxman m900 and others do an initial class A then shift to class AB, but still sounds good. Vitus relative to its A, does not sound good in AB. Class AB amps like Spectral are faster but you won't get that fluid sound, you will get a very different sound. There are exceptions like Dan Agostinos and Mike's Dartzeel which sound very good in AB

                  Some push pull tube amps are A, most SE amps are A.

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                  • MylesBAstor
                    MylesBAstor commented
                    Editing a comment
                    While I agree with the Vitus comments, they also have to be taken in light of it takes hours for the unit to really warm up and sound its best.

                    The Audia Flight is A/B but biased for like 10 or so watts in A IIRC. The amps got pretty hot and the kitties thought they were the nicest sauna.

                • #10
                  Amps can be class A or AB regardless of tube or solid state.

                  Class A traditionally has less distortion but is usually less efficient.

                  Now for the nuances:

                  There are two forms of class AB in tubes. AB1 and AB2. The difference is grid current. In a class AB1 amp, there is no grid current, just like an a class A1 amp. AB2 of course makes more power and potentially more distortion.

                  In solid state, its simply AB and the big question is where the amp goes from A to AB. Regardless of where it does this, its an AB amp. There is no such thing as 'enriched AB' or the like in engineering terms- that's just marketing.

                  It gets worse! Those reading carefully may have noticed my use of 'A1' above. Its also possible in a tube amp (single-ended or push-pull) to build an amplifier that is class A2. This is an amplifier where the outputs conduct all the way through the cycle up to full power, but during part of the waveform grid current is present. A2 allows for considerably more output power than a class A1 amplifier, but not as much as class AB1. (Our amps are class A2.)

                  The grid current thing means that the driver circuit has to be designed to be able to manage the current in the grid circuit.





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                  • #11
                    Holy cow I got a migraine reading your post but do very much appreciate the post. I use Aragon's 8008BB ON my setup input is balanced. I read they are class up to about 26 watts. Is this true class purely like a class a amp that stays in class a. ??

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                    • #12
                      I could fry eggs on a Nelson Pass SS clone amp!

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                      • #13
                        This article may help clear up some misconceptions about different classes of amplifiers.

                        http://www.audioholics.com/audio-amp...lifier-classes
                        McIntosh MC452, D150, MCT450 - Klipsch P-37F and PMC MB2 SE -(Wireworld cabling)

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                        • #14
                          Originally posted by WKM View Post
                          This article may help clear up some misconceptions about different classes of amplifiers.

                          http://www.audioholics.com/audio-amp...lifier-classes
                          Thanks. BTW, since when are SET amps prone to hum? Maybe some cheap, kits but not any that I've heard.
                          Myles B. Astor, PhD, Administrator
                          Senior Editor, Positive-Feedback.com
                          ________________________________________

                          Magico S5 Mk.2 speakers, cj ART300 40th Anniversary monoblock Amplifiers; cj GAT preamplifier Series 2; Doshi V3.0 phonostage; VPI Vanquish turntable/12-inch 3D tonearm/Lyra Atlas SL, Fuuga, vdh Colibri Signature, MOFI Master Tracker, Fuuga cartridges; Technics RS1506 with Flux Magnetic heads/Doshi V3.0 tape stage run balanced; Assorted cables including Transparent XL Gen. 5, Skogrand, Viero, Kubala-Sosna, MG Audio, Audience Au24SX, Genesis Advanced Technologies Power Cords. Stillpoint Aperture panels, MPod Magico feet, Cathedral Sound panels, Furutech NCF Nano AC receptacles; Silver Circle Tchaik 6 PLC. Symposium ISIS and SRA Craz racks; Audiodharma Cable Cooker; Symposium Ultra and assorted SRA platforms.

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                          • #15
                            My amps (CH Precision M1s) are A and AB, Pure Class A for the signal stages and AB for the power section. Power supplies are totally separate and each chassis requires two power cords, one for each. Over the years I personally preferred Lamm's A/AB M2.2 over the M1.2 Reference just because of the bass. I could get close to the 1.2's midrange with Valvo and Amperex tubes. When listening just to classical or Jazz the majority of the time the M2.2s are running in its A bias range anyway. It is with non-acoustic music where suddenly my speakers start gobbling up watts like a pothead eats up Cheetos. There's something about guitar amps and layer upon layer of artificial reverb that eats all this power up.

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